v1.8.8

Note: the packages generated by github (Source code links) do not contain the submodules. Use geogram_1.8.8.tar.gz or geogram_1.8.8.zip instead to get everything.

Fixed a small GLSL bug that prevented thick lines shader to compile with some OpenGL drivers (see #54).

Full Changelog: v1.8.7...v1.8.8